2.4 Monitoring Earthquakes




Vocabulary



Creep Meters- can measure the movement along a slip-strike fault
Laser-Ranging Devices- a device that measures changes with a laser beam and a reflector
Tiltmeter- measures tilting of the ground; works kind of like a carpenter's level
Satellite Monitor- uses radar to take pictures of faults


Outline


Devices that Monitor Faults

  • geologists use instruments to measure stress and deformation in the crust
  • Creep Meters
    • uses a wire stretched across a fault to measure horizontal movement along the fault
    • one side of fault-wire anchored to post
    • on other side, wire is attached to weight that slides if fault moves
  • Laser-Ranging Devices
    • uses a laser beam to discover tiny fault movements
    • calculates changes in time needed for the laser beam to travel to a reflector and bounce back
    • can detect any difference in change through the beam
  • Tiltmeters
    • measures tilting of the ground
    • includes 2 bulbs filled with liquid and is connected to/by a hollow tube
    • if land rises/falls the liquid will flow from one bulb to another
    • in bulb is a measuring scale that measures the depth of liquid in bulb
  • Satellite Monitors
    • satellite bounces radio waves off the ground
    • satellite records the echos of the waves that bounced back into space
    • amount of time it took for the radio waves to make their way back and forth is the precise measurements of distance to ground
    • geologists can detect small changes in elevation

Monitoring Risk in the United States

  • geologist can't predict when and where the earthquake will strike
  • but geologists can determine earthquake risk by locating where faults are active and where past earthquakes have occurred
  • highest risk areas in the United States:
    • Pacific Coast:
      • California
      • Washington
      • Alaska


Diagram(s)


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